The present application relates to apparatus for measuring the rate at which particles suspended in a transparent solution comglomerate and to a special purpose application of this apparatus.
As is known, human red corpuscles when in the presence of certain eggwhite bodies of blood plasma combine into large aggregates. These aggregates are the so-called money rolls (international terminology: "rouleaux"). This is the cause of the suspension lability, i.e., the sedimentation of the red blood corpuscles in the standing blood made viscous. One of the routine examinations most frequently used in medicine rests on the determination of the sedimentation rate, i.e., the determination of the settling rate of the blood corpuscles in cylindrical glass tubes. The methods used were disclosed by Westergren or by Wintrobe. Whenever the composition of the plasma eggwhite bodies is interfered with in a characteristic manner, there is an increased aggregation, (that is) large aggregates are formed, which will settle faster in accordance with known laws of physics (Stoke's law of sedimentation).
It is further known that in the presence of sufficient forces, for instance in the flow condition, these aggregates are again dispersed, to reform again at once upon termination of the forces. The process of aggregate formation therefore is arbitrarily reversible.
Conventional measurement of the blood aggregation potential is obtained from blood subsidence, 4 ml of blood being taken from the patient's arm vein and mixed with 1 ml of coagulation-inhibiting solution. Then this diluted blood is drawn up to a height of 200 mm in special tubes. The tubes are placed in the vertical position. Because of the downward sedimentation of the erythrocytes, which is influenced by the upward flow of the blood plasma, there is a reference level of red blood corpuscles with respect to the cell-free plasma. The number of mm by which this level drops after 1 and after 2 hours is read off and allows conclusions regarding illnesses.
This process requires a relatively large amount of blood, and furthermore is time consuming and is subject to spurious effects because of many different factors, and there have been many attempts to record the scope and the aggregation rate of red blood corpuscles in other ways. Thus the text "Oxymetrie, Theorie und Klinische Answendung" (Theory and Clinical Application of Oxymetry) by George Thieme publishers, Stuttgart, at pp 117-119, reveals the method of first rapidly stirring blood in a photometer and then measuring the decrease in reflection of the blood when there is no flow, this decrease being caused by the conglomeration of red blood corpuscles. However, the theoretical basis of these methods is uncertain.
Attempts furthermore have been undertaken to measure the influence of the aggregates on the apparant blood viscosity for slow flow by means of highly sensitive rotational viscosimeters.
Lastly, several attempts have been disclosed to accelerate the sedimentation rate by using either sedimentation tubes at an angle or else by subjecting the tubes to stronger forces in centrifuges.
All of the methods cited suffer from the drawback that they record only the consequences of the aggregation but not the aggregation process itself. These consequences vary extremely depending on the different measurement techniques used, and fundamentally may not be circumvented. Essentially this is so because the magnitude of the aggregates do not remain constant during sedimentaion and these aggregates are affected by the plasma flowing past them. Furthermore, the number of red blood corpuscles varies from patient to patient and hence affects the size of the aggregates as well as the space available to them in a complex manner. Unraveling effects between the thick suspension of aggregates and the thin blood plasma appreciably interferes with the measuring process of viscosimetry.